Next story in Science

Yawns spread more easily between family and close friends, and
from high-status monkeys to those lower on the totem pole,
according to a study published online today (Nov. 14) in the
journal PLoS ONE. This pattern of social yawning mimics one found
in humans and suggests infectious yawning is a byproduct of
empathy, which coordinates emotions in a group.

"It underlines that the mechanism of yawn contagion in the two
species is the same," said study co-author Elisabetta Palagi, a
primate researcher at the University of Pisa in Italy. "One of
the possible functions of yawn contagion is to synchronize
individuals of a social group. In humans, yawn contagion is
extremely important but just between people who share strong
bonds."

Many animals spread yawns: Chimpanzees and baboons catch them
from each other, dogs
can catch yawns from their owners, and even parakeets yawn
contagiously.

In humans and chimpanzees, contagious yawning follows social
rules: People
yawn if friends do, but not if a complete stranger does.
Those who haven't mastered empathy, such as babies (of the human,
canine and chimpanzee varieties) don't yawn infectiously, and
neither do
children with autism.

Because the infectiousness of yawning depends on social ties,
scientists have argued it is a byproduct of empathy, or the
ability to understand someone else's emotions, Palagi told
LiveScience. The same mechanism may underlie other emotional
contagions, such as infectious
laughter and smiling.

To see whether bonobo yawns spread like human ones, Palagi and
her colleague Elisa Demuru recorded 12 bonobos for three months
as they groomed each other, had lots of sex, played, fought and
made up at the Apenheul Primate Park in the Netherlands. During
that time, adult monkeys yawned 1,260 times. Each time one of the
apes opened its mouth to yawn, the team watched to see if another
bonobo did so within three minutes.

As in humans, Palagi's team found that yawns were more infectious
between close friends or kin, and between male and female
bonobos. (They used food sharing and grooming behavior to
determine which bonobos were best buddies).

Interestingly, yawns also spread from the top banana bonobo to
those of lower status.

The findings support the idea that
contagious yawning is a form of basic communication that
relies on empathy.

To follow up, the team wants to see if yawns spread more easily
depending on the relationship between apes — for instance,
between mother and son. They also want to see if yawn quantity
and quality affect their infectiousness, Palagi said.

"If you emit three or four yawns, are you more able to infect me
compared to other people who just emit one?"